1. Field of the Invention
The present invention relates to an apparatus for measuring the degree of entanglement in an entangled multifilament yarn.
2. Description of the Prior Art
As a method for giving cohesion to a multifilament yarn, a method for giving entanglement to single filaments which constitute a multilfilament yarn instead of giving twist is known. Since the entanglement in a multifilament yarn is easily obtained by disposal of the yarn in a turbulent flow of pressurized fluid such as compressed air, entangled multifilament yarns and apparatuses for their production are widely adopted in the textile industry. To indicate the degree of cohesion of a multifilament yarn due to such entanglement, a measure, generally called the degree of entanglement, is widely used.
Various methods for measuring the degree of entanglement in a multifilament yarn have been proposed. Of the conventional methods, one using the hook-drop test, such as the method disclosed in U.S. Pat. No. 2,985,995, is not only one of the most popular methods, but one of the best methods for measuring the pitch of points of entanglement (the length of opening) and the strength of entanglement.
This Hook-drop method is a method, wherein a hook with a weight is inserted through a multifilament yarn, and the degree of entanglement is determined on the basis of the distance through which the hook falls along the yarn on account of the weight of the hook.
The methods for performing automatically such measurement of the degree of entanglement due to Hook-drop method have been proposed from the view point of decreasing the measuring manpower, for instance, the method disclosed in U.S. Pat. No. 3,290,932 and the method disclosed in JP-A No. 52-53049.
However, there are several problems in such methods for measuring automatically the degree of entanglement. That is, there is the problem that a high performance and expensive tension meter is required to measure with high accuracy, whereby disadvantage on cost occurs, the problem that calibration of a tension meter is necessary, so that measurement takes a long time to measure, and the problem that errors may occur due to drift of the tension meter.
On the other hand, a method not needing a tension meter is disclosed in JP-A No. 58-115170. In this method, as shown in FIG. 23, a rotation meter 202 is connected to a pulley 201 which is free to rotate, and a needle 203 pierces the multifilament yarn Y threaded on the pulley 201. Weights 204a and 204b with a hook are hung respectively over the yarn Y positioned at both sides of the pulley 201, and electromagnets are built in the weights 204a and 204b respectively. Under the weights 204a and 204b, weights 206a and 206b constructed of magnetic material are provided, and the weights 206a and 206b are carried by carrying means 205a and 205b capable of moving in the vertical direction. Then, under the state of piercing the needle 203 into the yarn Y, the weights 206a and 206b are attracted to the weights 204a and 204b in turn, the yarn Y is moved in both directions over the pulley 201, and thereby the degree of entanglement of the yarn Y is determined.
However, in the above method, since it is necessary to place the weights 206a and 206b at a position under the weights 204a and 204b such that there is no interference with the vertical movements of weights 204a and 204b, enlargement of the apparatus in a vertical direction can not be prevented. Moreover, there is the problem, that it is rather difficult to stop the weights 206a and 206b always within the sphere of magnetic attraction of the electromagnets without contacting with weights 204a and 204b, in spite of change of the settled positions of weights 204a and 204b in accordance with the pitch of points of entanglement (the length of opening) in the multifilament yarn Y. For instance, in the condition wherein two weights 204a and 204b with a hook are balanced at both sides of the pulley 201 under the state of hanging the weights 204a and 204b, if the weight 206a or 206b having been carried upwards collides with one of the weights 204a and 204b, the weight 204a and 204b becomes unbalanced by reaction due to the collision, and the weight 204a or 204b may be raised to a position outside of the magnetic attraction. In that case, the weight 206a or 206b can not be attracted to the weight 204a or 204b, and the measurement of the degree of entanglement can not be continued.